Electrical musical instrument



May 6, 1941. HAMMOND 2,241,363

ELECTRICAL MUSICAL INSTRUMENT Filed July 24, 1940 2 Sheets-Sheet 1 Q I I I I I H I P0 WEE AMPLIFIER w ""T 1 WI:

Laurensfiammona May 6, 1941.

L. HAMMOND ELECTRICAL MUSICAL INSTRUMENT Filed July 24, 1940 ,odgg'g gg l Lhu 38 60 /6 {80 gaz 2 Sheets-Sheet 2 f/z/el? to I Z aur'ens' Hammond ..ha May c', 1941 muss ELECTRICAL musical. use-ramm- Laurens Hammond, Chicago, Ill. Application July :4, 1m, Serial No. 34mm 14 mm (or u-u-n My invention relates generally to electrical musical instruments, and more particularly to improved keying circuits for such instruments whereby new and interesting musical results may be obtained It is an object of my invention to provide an electrical musical instrument having a manual and a single pedal, wherein the single pedal is operative to cause playing of a note diflerent from but related to the lowest note being played on the manual. I

A further object is to provide an improved electrical musical instrument having a relatively small number of frequency sources which can be played easily by a pianist without necesitating learning of a pedal technique, to produce rich, full organ music.

A further object is to provide an improved keying circuit for electrical musical instruments in which the contemporaneous closure of two switches is required to cause sounding of a note, and in which one of the switches is controlled by a manual key, while the other switch is controlled by a pedal.

A further object is to provide a simple electric organ which may be manufactured at low cost, and which will adequately serve as a practical instrument for the playing of hymns and similar relatively simple musical selections.

Other objects will appear from the following description, reference being had to the accompanying drawings in which:

Figure l is a circuit diagram showing representative portions of the complete instrument;

Figure 2 is a circuit diagram illustrating a modified form of the invention; and

Figure 3 is a circuit diagram of a further modifled form of the invention.

For the rendition of hymns and similar liturgical selections, it is not essential that an organ have available a variety of tone colors, or that its manual have a range as 'great as that of a standard organ. A statistical survey of a number of hymnals shows that the range of notes scored in hymns seldom, if ever, are above the note B4 (987.77 0. p. s.) or notes below C1 (65.406 0. p. s.), so that a four octave manual covering the note range from C1 to B4 is fully adequate for the rendition of this type of music.

In playing hymns and the like, a proficient organist will almost invariably play such selections using full organ" registration, especially when the selections are played as accompaniment i'or congregation or choir singing.

Despite the fact that hymns are ordinarily not scored with notes below the note C1, the experienced organist will almost invariably use the pedals to provide a bass accompaniment for the music as scored. and such bass accompaniment notes will usually be one or two octaves below .the lowest note scored in the bass clef. Such pedal accompaniment adds greatly to the musical effect, and is one of the main characteristics (in .addition to intensity or volume) which distine guishes pipe organ and full electric organ music from reed organ music, when the instruments are being used for the rendition of liturgical music.

Furthermore, in many small churches and similar institutions, there is not available within the means of the congregation, a trained organist, and the playing of the organ is usually delegated to a pianist who is not skilled in the pedal technique or in the registration which are necessary for competently playing an organ. The use oi a pipe organ or full electric organ is therefore limited by the lack of trained organists.

These factors are conducive to the conclusion that many a small church, or the like, would have its musical requirements fully satisfied by a small electric organ limited in pitch range and tone colors available, but which would produce the low bass note accompaniment characteristic of standard pipe and electric organs without requiring the organist to be skilled in organ pedal technique or organ registration. The instrument described and claimed herein admirably fulfills these requirements, namely, simple construction, low cost, suiilcient range to render liturgical music, bass pedal accompaniment eflects, without requiring a pedal technique, and omission oi register controls, which latter are not necessary for the rendition of liturgical music and which are frequently misused by unskilled organists.

Briefly, the invention comprises a keying system for instruments of the organ type in which a single pedal operated switch is provided to control the sounding of a note which is harmonically related to the lowest note represented by the depressed keys in the bass register of the manual. The pedal is spring-returned and thus does not operate as an organ stop, but i the means for controlling the sounding of the harmonically related note which may be, for example, one octave or two octaves below the lowest note of a chord beng played in the bass register of the manual.

The invention differs fundamentally from the so-called "melody-octave-coupler arrangements sometimes employed in pipe organs, in that the player may easily control the sounding of the pedal note, determine the duration of the pedal note independently of the duration of the lowest note beng played on the manual, and because the manual playing technique is not rendered dimcult as it is when the melody-octave-coupler of a pipe organ is used. In the latter instance, the player must be very careful when playing a chord to make certain that the highest key of the chord is depressed slightly prior to the remaining keys, and is the last of the keys of the chord to be released. This technique required for the playing of the pipe organ using a melody-octave-coupier is difllcult to acquire, and even a very skilled organist will, in endeavoring to use this technique, frequently fail to depress the highest key of the chord before the other keys are depressed, or to release the highest key of the chord only after the other keys have been released. Such failure results in the sounding oi an arpeggio of undesired notes, which is very disturbing to the musician as well as to his audience.

As distinguished from this diillcult technique required in playing pipe organs equipped with melody-octave-couplers, the musician playing on an instrument incorporating my invention need merely "beat time" upon a single pedal with his foot as he plays the selection in an otherwise normal manne and by so doing he will control the sounding of the harmonically related pedal tone. Furthermore, the musician, while holding a given chord on the manual, may cause repetition oi the pedal note merely by repeatedly depressing the pedal. Similarly, the pedal note may be sounded or not sounded with the base chord of the manual merely by operating, or refraining from operating, the pedal,

As shown in Fig. i, the instrument comprises a manual consisting of a plurality of keys is, which, in Fig. 1, also hear their respective note designations C1 to E1, 02:, D2, B2, C3, and B4, these keys being representative of the complete series of keys from C1 to B4. There is likewise diagramatically shown, a plurality oi? electro= static generators, generating impulses of the fundamental frequencies of the keys C to B4 in elusive. Each of the generators comprises a wheel I2 and an electrode If, the note pitch designation corresponding to the note frequencies which the wheels are designed to produce, being indicated upon each wheei. It will be understood that electrostatic generators are shown merely for the purposes of illustration, and that any other suitable electrical frequency or sound generating system may be employed. In the circuit of Fig. 1, as distinguished from the circuit of Fig. 3, hereinafter to be described, the generators, or parts associated therewith, must be of such character that the sounding of .the tones generated may be controlled by a direct current potential upon an element forming a part of, or associated with, each of the generators.

Each of the keys is adapted to operate a singlepole single-throw switch arm it which is adapt ed, upon depression of the key. to engage a bus bar IS, the bus bar 18 being connected, to an adjustable potential direct current source shown as a battery 20. The bus bar l8 may be common to all of the keys of the manual or may be made in sections, the potentials of which may be separately adjusted. The depression of any of the keys thus completes a circuit from the source 2!? through the bus bar i8, its key switch It, and its conductor 22 to an electrode H of the associated generator. The outputs of all of the generaof the note designation of its key.

tors are combined in a conductor 24 which is connected to ground through a load resistance 26, the potential changes across which are amplifled in a preamplifier 28. I

Tone and volume control devices ll of any suitable design and arrangement receive the signal from the preamplifier I8, modify it as desired, and supply it to the power amplifier I! which is connected to a loud speaker 84. Thus. upon depression of any one of the keys II for the notes C2 to C6, the electrode ll of its associated generator will have an energizing potential impressed thereon. but the connection between the conductor 22 and its electrode is is preferably such that the tone produced will have somewhat gradual attack and decay characteristics. This is accomplished by interposing between the conductor 22 and its electrode is, a network comprising a resistor RI between the conductor 22 and electrode l4, and a resistor R2 and condenser C8 connected in parallel between the electrode I4 and ground. Thus, the rate at which the potential upon the electrod i4 is built up is determined primarily by the relative values of the resistor RI and condenser Cl, while the rate of decay of the note is determined by the relative values of the condenser Cl and resistor R2.

The keys [0 for the two lowermost octaves oi the keyboard are each adapted to operate a single-pole double-throw switch in addition to and simultaneous with the operation of their switches it. Each oi the single-pole doublethrow switches comprises a switch arm 38, an upper contact 38, and a lower contact 40. The switch arm 38 for the note C1 is connected by a conductor 42 to a switch 4%, which is arranged to be closed upon the depression of a single bass pedal 46, the switch H being connected to an ad justable direct current potential source illustrated as a battery 48. The pedal 45 is diagrammatically illustrated as being pivoted, and provided with a retum spring The remaining switch arms 3&5 are each connected to the upper contact 33 of the switch for the next adjacent lower note, so that when none oi. the keys is depressed, all of the upper contacts 38 of the 7 as will be interconnected by the switch the lower contacts 49 is connected to an, electrode M of a generator generating a i'requencz, one octave or two octaves below that Thus, the key it? for the notes Cit and C23? have their lower switch contacts Git connected to the generator l2 for the note COt. The connection between the lower contact 40 and electrode 5-2 is preferably through a resistance and capacity network which may comprise a series resistor R3, a shunt resistor RE connecting the contact so to ground, and a condenser C9 connected between the electrode i-G and ground.

From the foregoing it will be apparent that whenever any keys from C1 to B2 is depressed, the lowermost of the keys within this range which is depressed will, through its switch arm 3%, connect its lower contact 4|! to the polarizing potential source 48 provided the bass pedal 46 is depressed. All of the switch arms 36 of the depressed. keys, other than the lowermost key depressed, will be ineffective because of the series arrangement of the single-pole doublethrow switches.

The rate of attack of the tones produced by the generators If: for the notes C0 to B0 will be samba amass determined by the relative valuesof the resistor R8 and condenser C9, while the rate of decay will be determined by the sum of the resistances R3 and R4 relative to the value of the condenser C It will be noted that while two octaves of the keys of the manual, namely, C1 to B2, are capable of controlling the production of a bass pedal accompaniment note, only one octave of bass note generators is provided, and that therefore the lower contacts 40 for corresponding notes in the two lowermost octaves of the manual are connected respectively to a common generator. For example, it will be noted that the lower contacts 44 for the keys C18 and C2i are both connected to the electrode l4 for the generator which gencrates impulses at a pitch of cot, and similarly, the lower contacts 40 for the keys Di and D2 are both connected to energize the generator of pitch D0.

Of course if desired, any other suitable arrangement of the connections from the lower contacts 40 to the generators could be utilized. For example, the lowermost contacts 40 for the keys in the second lowermost octave could be connected to energize the generator for a note one octave lower instead f tWO octaves lower,

e. g., the contact 40 for the key D2 could be connected to the energizing circuit of the generator for note D1.

In playing the instrument as in the rendition of a hymn, the selection will be played upon the manual keys iii in the usual manner, and the player-will, whenever a bass accompaniment note is desired, depress the bass pedal 46'. Depression of this pedal 46 will automatically cause sounding of a bass note one or two octaves below the lowest note of the keys depressed on the manual (providing such lowest note is within the range C1 to B2), thus providing an adequate bass accompaniment which, in most instances, will be identical with that which the player might use if he had a full range of organ pedal notes available. In order to prevent the sounding of unwanted notes, the player will preferably depress the bass pedal 46 for each bass note desired. If this were not done, it is possible that the player might not release the keys on the manual simultaneously, and if the lowermost key depressed were released before other keys (within the range 01 to B2) such other keys would cause the sounding of their associated bass accompaniment notes. Thus, in the preferred method of playing the instrument, the pedal will be depressed an instant after the manual keys have been depressed, and the pedal released an instant before the manual keys are to be released. When the instrument is played sufliciently rapidly, e. g. from one chord to the next, the bass note of the first chord may not have decayed to inaudibility before the bass note of the next chord is sounded, thus providing a legato type of bass accompaniment even though it is obviously impossible to operate the bass pedal in a. legato manner.

It will be understood that it is not essential that the generators controlled by the single-pole double-throw key switches be one or two octaves below, but merely that they be harmonicall'y related to the pitches oi the keys by which they are controlled.

From the foregoing it will appear that I have provided a very simple form of electrical musical instrument capable of the rendition of customary liturgical music in a conventional organlike manner, without the necessity of providing the usual pedal clavier, and without making it necessary for the player to acquire pedal technique or to become proficient at organ registration. It will be .understood that the generators employed are preferably such as will produce a tone characteristic of full organ," so that the music produced in the playing of hymns and. the like, will be the equivalent of that which would be produced by a relatively large and expensive organ when registered for the playing of liturgical music. To further this result, the generators may be designed to produce complex tones, each containing not only the harmonic partials of the 8 ft. pitch, but also some of the harmonics of the 4 ft. pitch, or the 16 ft. pitch, or both.

In Fig. 2, I have disclosed representative portions of an instrument employing a slightly modifled circuit. Such elements of the modification of Fig. 2 which are similar to those previously described, have similar reference characters applied thereto and will not be again described. The addustable direct current potential source 44 is connected by a current limiting resistor Rl to ground through a normally closed switch II, which is adapted to be opened upon depression of the bass pedal 48. The resistor R5 is also connected between conductor 42 and the potential source 40 so that when the bass pedal is depressed, the potential from the source 4| will be impressed upon the conductor 42, and thus be available for the energization of the bass tone generators. The modification shown in Fig. 2 will be played in a manner as described above with reference to the construction shown in Fig. l. d

In Fig. 3 I have illustrated the invention as applied to an electrical musical instrument in which the tones are controlled by keying signals produced by continuously operating generators. The diagram of Fig. 3 is thus representative of the application of the invention to electrical instruments in which signal generators are employed, and in which the output of the generators is transmitted to the output circuit of the instrument under the control of key operated switches, as distinguished from the construction shown in Figs. 1 and 2, wherein the outputs of the generators are controlled by key operated switches controlling energizing circuits for the generators.

Such of the elements of the modification of Fig. 3 which are similar in construction and function to parts previously described, have had corresponding reference characters applied thereto.

The signal generators comprise tone wheels 52 made of magnetic material and having projections on their peripheries rotating in close propinquity to wedge-shaped ends of permanent magnets 54 in a manner similar to that disclosed in my aforesaid Patent No. 1,956,350. For the present purposes, however, the peripheries of the tone wheels 82 are formed to produce a complex wave form of considerable harmonic development.

Generators CI to El, C28, D2, B2, B3, and B4 are shown as representative of a complete set of generators for the notes C1 to B4 while generators C0 to Eli and B0 are illustrated as representative of the twelve pedal tone generators for generators for the notes C1 to B4, while generators has a winding 56 around its permanent magnet 54, one end of the winding being grounded, while the other end is connected through a current limiting resistance It to its associated key operated switch It. The key operated switches ii are adapted to make contact with a bus bar which is connected by a conductor 52 to a selected one of a plurality of taps on a primary winding 84 of an output transformer 88, the secondary ll of which is connected to a tone and volume control apparatus 10, and thence through a preamplifier l2 and power amplifier 14 to a loud speaker".

Upon depression of any one of the keys I, a signal from its associated generator will be transmitted to the output circuit, amplified, and translated into sound. Each of the keys, in addition to operating its switch l8, operates its associated switch arm 36. As will be apparent, these keys are so arranged that the lowest of a plurality of depressed keys will select a generator either one octave or two octaves below the pitch of the lowermost depressed key, and connect its output to conductor 18. The conductor 18 is adapted to be connected through a conductor 19 to a selected tap on the primary 64, upon closure of a switch 80 operable by depression of a spring-returned pedal 82.

From the foregoing description it will be clear that the instrument illustrated in Fig. 3 will be operative to produce results similar to those obtained by the instrument shownin Figs. 1 and 2, namely, the sounding of a note, under control of the pedal 82, which is one or two octaves lower in pitch than the lowermost note being played on agiven section of the manual. The relative intensities of the tones produced under the control of the manual and those produced under the con trol of the pedal 82, may readily be controlled by the selective connection of the conductors 62 and 19 to different taps on the transformer primary 64.

In the embodiments illustrated and described herein, the circuit arrangement is, in'each instance, of a type such that the lowermost of a plurality of keys depressed controls the pitch of the tone controlled by the pedal. It will be clear that the arrangement of the single-pole doublethrow switches operated by the keys could readily be reversed so that the highest depressed key of the manual would control the pitch of the tone produced by depression of the pedal. Such latter arrangement might be of musical usefulness in some instances, although in the majority of cases, the arrangement disclosed will be more useful.

As previously intimated, the generators may be of any suitable type which may be energized under the control of the playing keys, or the output of which may be controlled by the playing keys. Representative generators of this class are disclosed in my prior applications Serial No. 157,969, filed August 7, i937 and Serial No. 281,077, filed June 26, 1939, or in any one of the following patents: Nos. Re. 21,137, 2,126,464, 2,126,682 and 1,956,350. In their broader aspects, the principles of my invention may also be applied to instruments having an electrically controlled sound generator for each note.

It will be further understood that while in the preferred form of the invention the accompaniment tone is one which is an octave or two octaves below the lowermost of the bass register manual keys depressed, the principles of the operation of the invention may also be employed in a manner such that a note higher than the highest depressed key on the manual, but harmonically related thereto, will be sounded. The underlying principle of the invention is that an additional manually or pedally operated control is provided which, when operated, will cause the production a note which differs i'rom, but is harmonically related to, a note produced by depression of a key of the manual.

While I have shown and described particular embodiments of my invention, it will be apparent to those skilled in the art that numerous variations and modifications are possible without departing from the underlying principles of the invention. I therefore desire, by the following claims, to include within the scope of my invention, all such variations and modifications by which substantially the results of my invention may be obtained by substantially the same or similar means.

I claim:

1. In an'electrically controlled musical instrument, the combination of a manual having a plurality of depressible keys, a musical tone generating system controlled by said keys, an accompaniment tone generating system, means controlled by the endmost of a plurality of simultaneously depressed keys of said manual to select the pitch of the tone to be produced by said accompaniment tone generating system, a single normally ineffective control element, and means operated by said control element to render said accompaniment tone generating system effective to produce the tone of selected pitch,

2. In an electrically controlled musical instrument, the combination of a manual having a plurality of depressible keys, a musical tone signal generating system controlled by said keys, an accompaniment tone generating system, means controlled by the lowermost of a plurality of simultaneously depressed keys of said manual to determine the pitch of the tone to be produced by said accompaniment tone generating system, a pedal, and means operated by said pedal to render operative said accompaniment tone generating system.

3. In an electrical musical instrument, the combination of a manual comprising a plurality of keys, a tone generating system controlled by said keys, a plurality of accompaniment tone generators of pitch lower than that represented by the lowest key of said manual, means operated by the lowermost of a plurality of said keys which are simultaneously depressed to select one of said accompaniment tone generators for operation, a pedal, and means operated by said pedal for rendering the selected tone generator effective to produce its tone.

4. In an electrical musical instrument, the combination of a manual comprising a plurality of keys, means controlled by said manual for produclng musical tones, means for generating accompaniment tones, means operated by said keys to determine which of said accompaniment tone generators is to be rendered operative, a bass pedal, and means controlled by said bass pedal to render operative the tone generator selected by said keys.

5. In an electrical musical instrument, the combination of a. manual comprising a plurality of keys, means for generating tones corresponding respectively to the keys of said manual, means for generating tones of pitch beyond the range of said manual, 9. control element for said additional generators, resilient means to maintain said control element in ineffective position, and means conjointly controlled by said manual keys and said control element to cause sounding of one of said additional generators.

6. In an electrical musical instrument, the combination oi a manual comprising a plurality of keys, means controlled by depression of said keys to cause sounding of notes corresponding to the keys, a single bass pedal, means biasing said pedal toward an ineffective position, and means operated'by said pedal to control the sounding of a note which difiers in pitch from but is harmonically related to the note corresponding to the lowermost of the depressed keys of said manual.

7. In an electrical musical instrument, the combination of a manual comprising a plurality of keys, means controlled by said keys to cause the sounding of notes corresponding in pitch to said keys, a bass accompaniment control element, and means comointly controlled by said element and the lowermost of any of a plurality of keys depressed on said manual to cause the sounding of a note harmonically related to but lower in pitch than the note corresponding to said lowermost depressed key.

8. In an electrical musical instrument having an output circuit, a manual comprising a plurality of keys and a signal generating system controlled by said keys, an accompaniment tone generating system, a single pedal, and means controlled conJointly by said pedal and said keys to cause transmission to the output of the instrument of a tone signal from said accompaniment tone generating system. I

9. In an electrical musical instrument, the combination of a manual including a plurality of keys, a signal generating system controlled by said keys, a series of single-pole double-throw switches operable respectively by keys of said manual, a plurality of accompaniment generators, means controlled by said switches for selecting one of said accompaniment generators, a bass pedal, and a circuit controlled by said bass pedal to render effective the generator selectedby said selecting means.

10. For use in an electrical musical instrument having an output circuit and a plurality of generators of electrical impulses of musical frequencies, a plurality of keys forming a manual, circuits completed by operation of said keys to cause transmission to the output circuit of the instrument of electrical impulses of frequencies corresponding to the operated keys, an additional set of electrical generators, a slow decay circuit associated with each of said generators of said additional set, means operated by said keys to select one of the generators of said additional set which is harmonically related to the lowest of a plurality of said keys which are simultaneously depressed, a foot-operated pedal, means to bias said pedal to inoperative position, and a circuit completed upon operation of said pedal to cause the transmission to said output circuit of impulses from the generator of said additional set which has been selected by said key operated means.

11. For use in an electrical musical instrument having an output circuit and a plurality of generators of electrical impulses of musical frequencies, at least twenty-four keys forming a manual, circuits completely by operation of said keys to cause on to the output circuit of the instrument of electrical impulses of frequencies corresponding to the keys. an additional set of electrical impulse generators of frequencies lower than the frequency of any of said first named generators and lesser in number than the keys of said manual, 9. slow decay circuit associated with each of said additional generators, means operated by said keys to select one of said additional generators which generates a frequency one or more octaves lower than the Irequency associated with the lowest of a plurality of said keys which are simultaneously depressed, a foot-operated spring-returned pedal, and means rendered efiective by operation of said pedal to cause transmission to said output circuit of impulses from the one of said additional senerators which has been selected by said keys.

12. For use in an electrical musical instrument having a plurality of keys, a plurality oi electrostatic generators, and attack and decay circuit elements for each of said generators, the combination of means controlled by each of said keys for impressing an exciting potential on the generator associated therewith through its attack and decay circuit elements, a conductor, means controlled by the lowest of a plurality of simultaneously depressed keys to connect said conductor to the attack and decay circuit elements of one of said generators of a frequency one or more octaves lower than the frequency represented by said lowest key, a source oi exciting potential, a foot-operated spring-returned bass pedal, and a switch operated by said pedal eiiectively to impress the potential of said source upon said conductor.

13. For use in an electrical musical instrument having an output circuit and a plurality of electromagnetic generators of electrical impulses of musical frequencies, a plurality of keys forming a manual, circuits completed by operation of said keys to connect selected generators to the output circuit of the instrument, an additional set of electromagnetic generators of lesser number than the keys of said manual, means operated-by said keys to select one of the generators of said additional set which is harmonically related to the lowest of a plurality of said keys which are simultaneously depressed, a footoperated pedal, means to bias said pedal to inoperative position, and a circuit completed upon operation of said pedal'to connect to said output circuit the generator of said additional set which has been selected by said key operated means,

14. In an electrically controlled musical instrument, the combination of a manual including a plurality of keys, a signal generating system controlled by said keys, switches operable respectively by keys of said manual, a plurality of accompaniment generators, means controlled by said switches for selecting one of said accompaniment generators, a bass pedal, a circuit controlled by said bass pedal to render efiective the generator selected by said selecting means, and means to bias said bass pedal to ineflective position.

LAURENS HAMIMOND.

CERTIFICATE OF CORRECTION, Patent No. 2,241,565. May 6, 19141.

LAURENS HAMMOND.

It is hereby certified that error appears in the printed specificatio; of the above numbered patent requiring correction as follows: Pagel, second column, line 51,,and page 2, first column, line LL, for "bug" read --being--; page 2', first column, line 55; for "base" read --bass--; line 5?, strike out the comma after "pedal" and insert instead a period; page 5, second column, line 69, strike out "generators for the notes C1 to, BL while" and insert instead -notes CO to B0 inclusive. .Each of the--;

pageh, first column, line 1, for "52" read --62-; page 5, first column, A

line 65, claim.ll,.for "completely" read --completed--; and that the said Letters Patent shouldbe read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 24th day of June, A. D. 19m.

Henry Van Arsdale, (Seal) Acting Commissioner of Patents.

CERTIFICATE OF CORRECTION, Patent No. 2,2h1,363. May 6, 191 1.

- LAURENS HAMMOND.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page l, second column, line 5 1, and page 2, first column, line )4, for "b eng" read --being--; page 2, first column, line 55', for "base" read --bass-; line 57, strike out the comma after "pedal" and insert instead a period; page 5, second column, line 69, strike out "generators for the notes C1 to, Big, while" and insert instead --notes CO to B0 inclusive. .Each of the--;

pagel first column, line 1, for "52" read -62-; page 5, first column,

line 65, claimll for "completely" read -completed--; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 21ml day of June, A. D. 19hr.

Henry Van Arsdale, (Seal) Acting Commissioner of Patents. 

